Transcript Metabolic Calculations - Purpose Estimate energy expenditure during steady state exercise

Metabolic Calculations Purpose
Estimate energy expenditure during steady
state exercise
Importance of Metabolic Calculations
• It is imperative that the exercise
physiologist is able to interpret test results
and estimate energy expenditure.
• Optimizing exercise protocols.
• Exercise prescription.
• Weight loss.
Metabolic Calculations (S=Speed in m/min; G= % Grade)
MODE
Horizonal
+ Vertical
+ Rest
• Walking VO2 = (0.1• S)
+ (1.8 • S • G)
+ 3.5
• Running VO2 = (0.2• S)
+ (0.9 • S • G)
+ 3.5
• Cycle VO2
= 1.8 (work rate) + 3.5
+ 3.5
Body Weight (kgs)
• Arm VO2
= 3 (Work Rate)
+ 3.5
Body Weight (kgs)
• Stepping VO2 = (0.2• f)
+ (1.33 • 1.8 • h • f) + 3.5
CARRY OUT EACH STEP TO 2 DECIMAL PLACES
Monark Cycle Work Rate: Resistance X Revs/min x 6m/rev
Monark Arm Work Rate: Resistance X Revs/min x 2.4m/rev
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1L= 1000 mL
1kg= 2.2 lbs
1mph= 26.8 mmin-1
1 MET = 3.5 mLkg-1min-1
1 W= 6 kgmmin-1
1 in = 0.0254m=2.54 cm
Pace: min/mile to mph = 60/time
Ex: 7.5 min/mile / 60 min/hr = 8mph
• Kcal/min = METS * 3.5 * BW
200
• 1L O2min-1 = 5 kcalmin-1
• 1 lb of fat= 3500kcal
Metabolic Calculations
(S=Speed; G=Grade)
• Walking (most accurate from 1.9-3.7 mph)
– VO2 = (0.1• S) + (1.8 • S • G) + 3.5
• Treadmill and Outdoor Running (for speeds > 5 mph)
– VO2 = (0.2• S) + (0.9 • S • G) + 3.5
• Leg Ergometry
– VO2 = 1.8 (work rate)/(BM) + 3.5 + 3.5
• Arm Ergometry
– VO2 = 3 (Work Rate)/(BM) + 3.5
• Stepping
– VO2 = (0.2• F) + (1.33 • 1.8 • H • f) + 3.5
CARRY OUT EACH STEP TO 2 DECIMAL PLACES
Assumptions and Limitations
• Measured VO2 is highly reproducible at a given steady
state workload. Failure to achieve steady state is an
overestimation of VO2.
• Accuracy of equations is unaffected by most
environmental conditions such as heat and cold.
• However, variables that change mechanical efficiency
(gait abnormalities, wind, snow or sand) result in a
loss of accuracy.
• Assumption that ergometers are calibrated and no
holding on to hand rails occur during on treadmill.
Met Calc - Key Points
2500
VO2 (ml/min)
• Estimates oxygen
requirement (VO2) for
various workloads
– Linear relationship
– Some variability
(S.E.E. 7%)
S.E.E. 7%
2000
1500
1000
500
assumptions
0
50
100
Watts
150
200
Met Calc - Key Points (con’t)
• “Steady State” or
submax exercise:
• “Maximal” Exercise
O2 cost > O2 uptake
Component
Predicted
O2 Requirement
O2 cost = O2 uptake
= Anaerobic
you cannot predict maximal
VO2max
VO2max
Max Exer
Workload
Met Calc - General Principle
Mechanical
Workload
• Meters.min-1
• kgm.min-1
Metabolic
Equivalent
• VO2
• METs
• kcals.min-1
We estimate one value based on
knowledge of the other
Metabolic Units
Gross vs. NET
All equations give Gross VO2 values.
For weight loss use the NET VO2 vales.
NET: Gross – resting value
VO2 NET : 40 ml/kg/min – 3.5 ml/kg/min = 36.5 ml/kg/min
OR
: 11.4 METS – 1 MET = 10.4 METS
Metabolic Calculations (S=Speed in m/min; G= % Grade)
MODE
Horizonal
+ Vertical
+ Rest
• Walking VO2 = (0.1• S)
+ (1.8 • S • G)
+ 3.5
• Running VO2 = (0.2• S)
+ (0.9 • S • G)
+ 3.5
• Cycle VO2
= 1.8 (work rate)
Body Weight
• Arm VO2
= 3 (Work Rate)
Body Weight
• Stepping VO2 = (0.2• f)
+ 3.5
+ 3.5
+ 3.5
+ (1.33 • 1.8 • h • f) + 3.5
CARRY OUT EACH STEP TO 2 DECIMAL PLACES
Monark Cycle Work Rate: Resistance X Revs/min x 6m/rev
Monark Arm Work Rate: Resistance X Revs/min x 2.4m/rev
ACSM Walking Equation
• Speeds 50-100 m/min; 1.9-3.7 mph
– (1 mph = 26.8 m/min)
• “Relative” VO2 unit (ml/kg/min; ml.kg-1.min -1)
VO2 walking = Horizontal Walking (HW) + Vertical Climb (VC) + Resting
VO2 walking = Speed (m/min) x 0.1 + % grade x Speed (m/min) x 1.8 + 3.5
ACSM Walking Equation
• Example: VO2 for walking @ 3.0 mph at 5% grade
• Convert 3.0 mph to m/min
– 3.0 x 26.8 = 80.4 m/min
VO2 walking = Horizontal Component + Vertical Component
+ Resting
VO2 walking = Speed (m/min) x 0.1 + % grade x Speed (m/min) x 1.8 + 3.5
• VO2 = 80.04 x 0.1 + 80.04 x .05 x 1.8 + 3.5
• VO2 = 8.04
+ 7.20
+ 3.5
• VO2 = 18.74 ml.kg-1.min-1
• VO2 = 18.74 ml.kg-1.min-1 / 3.5 = 5.4 METS
ACSM Running Equation
• Speeds > 134 m/min; > 5.0 mph (1 mph = 26.8 m/min)
VO2 for running at 6.0 mph at a 5% grade
• Convert 6.0 mph to m/min
– 6.0 x 26.8 = 160.8 m/min
VO2 running = Horizontal Component + Vertical Component
+ Resting
VO2 running = Speed (m/min) x 0.2 + % grade x Speed (m/min) x 0.9 + 3.5
VO2 running = 160.8
VO2 running =
x 0.2 + 0.05 x 160.8 x 0.9 + 3.5
32.16
+
7.24
+ 3.5
VO2 running = 42.9 ml/kg/min
VO2 running = 42.9 ml/kg/min / 3.5 = 12.26 METS
ACSM Leg Cycling Equation
• Loads 300-1200 kgm/min; 50-200 watts
Work Rate = kg x meters/rev x RPM
Use 6 meters/revolution for the Monark Ergometer
Add resting twice : 1 for resting and 1 for unloaded
Q: What is the VO2 for a 90 kg subject pedaling at 2.0 kgs at 60 rpms
Work Rate: 2.0 kg x 6 m/rev x 60 rpms = 720 kgm
VO2 Cycling = 1.8 x WR + 3.5 + 3.5
BW
VO2 Cycling = 1.8 x 720 + 3.5 + 3.5
90 kgs
VO2 Cycling = 14.4
+ 3.5 + 3.5
VO2 Cycling = 21.4 ml/kg/min or 6.1 METS
ACSM Arm Cycling Equation
• Loads 150 to 750 kgm/min; 25-125 watts
– 3.0 = ml.min-1 per kpm/min ( from leg cycling)
– Only 1 resting component (3.5)
– Monark™ Rehab Trainer: 2.4 meter/rev
Work Rate: kg x 2.4 meters/rev x rpm
Q: What is the VO2 of a 100 kg person who uses a
Monark arm ergometer at 3 kg at 50 rpms.
Work Rate: 3 kg x 2.4 meters/rev x 50 revs/min = 360 kgm
• VO2 arm=
+ 3.5 ml.kg-1.min-1
•
+ 3.5 ml.kg-1.min-1 = 14.3
3 x WR
BW
VO2 arm= 3 x 360
100
ml/kg/min
ACSM Stepping Equation
• VO2stepping =
0.2 x f + 1.33 x 1.8 x h x f + 3.5
• VO2 varies with Step height & rate
• “Relative” VO2 unit (ml.kg-1.min-1)
• VO2 (ml.kg-1.min- 1 ) = Horizontal + Vertical + Resting
• Horizontal = steps/min x 0.2
• Vertical = step ht x steps/min x 1.33 x 1.8
– Down cycle 0.33 VO2 of the up cycle (add this in by
multiplying by “1.33”)
– 1.8 is the constant for vertical work
• Step height is entered in meters
– 1 in = 0.0254m=2.54 cm
ACSM Stepping Equation
Q:
What is the VO2 for a 55 kg woman who is stepping on a 12”
bench at 30 steps per minute
• Calculate step height in meters
– 12” x 0.0254 = 0.31 meters
VO2stepping =
0.2 x f + 1.33 x 1.8 x h x f
+ 3.5
VO2stepping = 0.2 x 30 + 1.33 x 1.8 x 0.31 x 30 + 3.5
VO2stepping =
6
+
22.26
+ 3.5
VO2stepping = 31.76 ml/kg.min
VO2stepping = 31.76/3.5 = 9.1 METS
Question: What is the kcal expenditure (kcal.min-1) for this 55 kg
person exercising at the above VO2 or METS? This person
exercises at this rate 3 times per week for 30 minutes each
session.
Kcal conversion example
Q: What is the kcal expenditure (kcal.min-1) for a 55 kg person exercising at an
oxygen uptake of 9.1 METs? This person exercises at this rate 3 times per
week for 30 minutes each session. How long will it take this person to lose
10 pounds exercising at this rate?
kcal.min-1 = METs x 3.5 x BW (kg)
200
kcal.min-1 = 8.1 x 3.5 x 55
(Why did we use 8.1 METS?)
200
(For weight loss use the NET)
kcal.min-1 = 7.8
1 pound of fat = 3,500 kcals
10 pounds = 35,000 kcals
Answer: 35,000 kcals = 4,487.18 minutes
7.8 kcals/min
4,487.18 minutes = 49.9 weeks
90 minutes/week